7x - 3y = 4
2x - 4y = 1

the solution to the system of equations is

  
7x - 3y = 4 => 7x = 3y + 4 => x = (3y + 4) / 7    2x - 4y = 1 => 2x = 4y + 1 => x = (4y + 1) / 2
=> (3y + 4) / 7 = (4y + 1) / 2      (3y + 4) * 2 = (4y +1) * 7       6y + 8 = 28y + 7       22y = 1       Y = 1/22 =>you can substitute y for the system of equations and find   x